The researchers discovered a compound called harmine in hairs from an adult male and a one-year-old baby, who both date to sometime between A.D. 800 and 1200. Harmine can help humans absorb hallucinogens and may be a powerful antidepressant.

"These individuals probably ingested harmine in therapeutic or medicinal practices, some maybe related to pregnancy and childbirth," said study co-author Juan Pablo Ogalde, a chemical archaeologist at the University of Tarapacá in Arica, Chile.

"However, it is possible also that consumption of harmine was involved in religious rituals, said Ogalde, whose research appeared online October 14 in the Journal of Archaeological Science.

X-rays showed that the adult male—who was buried with items of social prestige such as panpipes, a four-pointed hat, and a snuffing tray—had damage near the nose, perhaps from sniffing.

As for the baby, Ogalde speculated that the mother had consumed the drug and passed it on to her offspring during pregnancy or breast-feeding.

"The fact this mind-altering substance was found even with a one-year-old shows how much a part of their life it was," said archaeologist Alexei Vranich of the University of California, Los Angeles, who did not participate in the study.

Habitual Users

The empire of the Tiwanaku once ranged from what is now northern Chile to southern Peru. (See a map of South America.) Between roughly A.D. 500 and 1000, they expanded from their origins on the Bolivian shores of Lake Titicaca via religious control and military might.

Elaborately decorated snuffing kits have been found in hundreds of Tiwanaku tombs. Archaeologists think these trays and tubes were used to inhale herbs, perhaps ceremonially.